1. Field of the Invention
The present invention relates generally to tree harvesters, and more particularly to tree harvesters of the type which combine the operations of shearing, delimbing, topping, and bunking of processed trees.
2. Description of the Prior Art
The prior art in tree harvesters includes U.S. Pat. No. 3,905,407 in which a horizontally disposed tree processing mechanism is mounted onto a wheeled and articulated frame and a tree transfer mechanism that includes a grapple and shear is mounted to one end of the tree processing mechanism. In operation, the grapple is secured to the tree near the ground, the shear severs the tree from its roots intermediate of the grapple and the ground, and the tree transfer mechanism horizontally positions the tree onto the tree processing mechanism.
In sequence, a processing clamp closes around the butt end of the felled and horizontally positioned tree, delimber knives close around the tree, the delimber knives move longitudinally toward the top of the tree stripping limbs therefrom as they move, topping knives remove the top of the tree, the processing clamp is opened, and the processed tree is dropped into a bunk on the side of the tree harvester.
A first flexible cable mechanism is used to reciprocably actuate an extendable beam member that is guidingly mounted on a first elongated beam member, and a second flexible tension mechanism is used to reciprocate the carriage on the extendable beam member, the delimber knives and the topping knives being carried by the carriage.
The delimber and topping knives are mechanically closed by springs and are mechanically opened by carriage movement. This mechanical actuation of the delimber and topping knives has the limitations of limiting the delimber and topping knife closing forces, precluding the maintaining of constant delimber knife closing forces versus changes in tree diameter, precluding easy adjustment of delimber knife closing forces that are required for different seasons, limiting the flexibility of automatic sequencing cycles, and requiring that the topping knives precede the delimbing knives.
In particular, it is desirable to return the carriage to the retracted position after topping a small tree without the carriage proceeding to the maximum log length, so as to reduce the cycle time of the machine.
Also, it is desirable for the topping knives to follow the delimbing knives because the topping knives are subject to jamming by limbs that are accumulated in front of the delimber knives if the topping knives precede the delimber knives.
The prior art also includes U.S. Pat. No. 3,924,667, of common ownership entity with that of the aforementioned patent and with the present invention, in which the processing clamp tilts upwardly before opening, facilitating the dropping of a processed tree into the bunk.
The complete specifications of both U.S. Pat. No. 3,905,407 and U.S. Pat. No. 3,924,667 are included in the specification of the present invention by reference herein thereto.